John Michael DiBianco, MD
In this interview Dr. John Michael DiBianco discusses why a mini-PCNL might be useful in a pediatric patient, describes his technique, and offers tips for performing the procedure. DiBianco is an assistant professor of urology at the University of Florida, Gainesville.
This transcription has been edited for clarity.
Who is the ideal patient for a pediatric miniPCNL?
In my opinion, no patient group benefits more from a miniaturized technique than a pediatric patient, which kind of makes sense. When you consider how small the kidneys are, and previously in many places we were using a 30 French size access, a very large burr hole access, compared to an adult kidney, that transition and that difference was usually quite large. So I think the patients that benefit the most are patients with certain types of stones that are potentially much more difficult to treat with some of the more minimally invasive procedures like ureterorenoscopy or shock wave lithotripsy. So large volume stones, according to the guidelines, and particularly in the lower pole.
The lower pole kidney is harder to reach with some endoscopes and has poorer drainage, so other techniques like shockwave lithotripsy are slightly less stone-free and less effective. Many patients, particularly children, often have to undergo many repeat procedures because of their small size. Let’s say you want to do a ureterorenoscopy and the endoscope is too big. It won’t fit into the ureter. You put in a stent, get anesthetic, and then you come back. Then you go up and try to remove all the stones. Maybe it’s too difficult. For some reason, you don’t get all the stones out in that procedure. Then you get another stent and come back.
Many of the patients we treat here have either had multiple procedures before or are at high risk of not having great success with one of these other minimally invasive procedures, such as shock wave lithotripsy or ureterorenoscopy. So many of my pediatric colleagues come to me to see if they are a good candidate for a miniaturized PCNL.
Please describe your technique for miniPCNL in pediatric patients.
Like anything else, when we do a PCNL, we go through the skin, through the back into the kidney, and we always do a CT scan. That’s pretty standard. First of all, that’s helpful to me because it classifies the stone volume, maybe even the density and all those things. But it also tells me if I have a window, an area where I can actually do this safely without hitting other things that might be in the way, like the bowel, the spleen, or other things you don’t want to put a hole in. So we always get that, and as long as there’s a window, we’ve been pretty successful in doing the procedure.
We usually put them in this modified supine position where we operate on the same side, the leg stays straight and the other leg is in a stirrup, so we actually have access from both sides, like a normal ureterorenoscopy, but also from the side where we’re going to do most of the percutaneous work. I use X-rays, I use fluoroscopy. That’s just how I was trained, that’s how I feel comfortable. We use as low a dose as possible because of course these are younger patients, so I’m certainly more concerned, at least for me, about how much radiation they’re getting. I know some colleagues who don’t use fluoroscopy and don’t use X-rays, they use ultrasound. I’m not as comfortable with that, so I don’t do that. But it’s certainly been described. We use a small catheter in the bladder, in the ureter, to inject contrast into the kidney. We use this contrast agent at the same time as an X-ray and fluoroscopy examination to see where on the skin we need to insert a needle to get into the kidney at the right place.
We use a lot of these different things to see where the best access is, what’s the safest, what’s the most successful, where we only have to make one puncture into the kidney. And once we’ve done that and we’ve been successful with that, we decide – usually preoperatively based on the stone volume – how big to make the hole. Miniaturized PCNL can be anywhere from 22 to 12 French, so we have a very wide range available to us. We use one of these kits, one of these tools that comes in several different sizes. The most common I use is an 18 or 16 French access, but it really depends.
If you look at our series, we’ve done about 8 patients so far. In one patient, we did it on both sides, so 9 renal units total, and we’ve gone from 16 French all the way up to 20 French with our sizes, so it really depends. Once we do that, we start working and usually the stone breaks up very well and we can take everything out through that port and they don’t need anything else through that hole, so we can close it. And usually, if the ureter allows it, we can also put an endoscope in from below because that positioning allows us to get between the legs and the flank easily. And we search the rest of the kidney ureteroscopically just to make sure we don’t miss anything. Then we leave a stent afterward. Sometimes we leave it on a string so the patient can take it out at home a week or so later, depending on how comfortable the family is, how cooperative the patient is, depending on their age.
We’ve been pretty successful here. I think the nice thing about this positioning is that in the past we’ve often done percutaneous surgeries with the patients prone, so they’re in a sort of Superman/Superwoman position. Sometimes when you run into problems, like a stricture or other anatomical problems, it’s a little more difficult to do your typical endoscopic ureteroscopic techniques in that position.
The beauty of the modified supine position is that you have all these techniques and tools at your disposal in an emergency. In children, we don’t see many stones, thank God, but when we do, there’s usually a reason for it. And often it’s anatomical. So I think it gives us the opportunity to do other things that may be necessary to treat that patient and that stone. Off the top of my head, I can think of about three patients who had an obstruction of the ureter-renal junction, whether it was a stricture or something else, that we had to treat at the same time as the stone. Some of them have altered anatomy, double ureters, duplex systems, and so on. So it gives us a lot of flexibility to tailor the surgery to the patient, rather than forcing the same surgery on them in a variety of clinical scenarios.
How did you come to learn miniPCNL?
During my residency, I learned how to do a standard PCNL on adults. Where I trained, we did fluoroscopy, and we did it in the prone position, kind of in this Superman position. When we rotated at Children’s National because I did my residency at George Washington in DC, we did maybe two PCNLs in the six months I was there, so not a lot. Fortunately, it’s not a very common problem. When I got my fellowship, I did a two-year fellowship in endourology to learn some more advanced stone and BPH techniques. I learned and was trained in the supine position, which was certainly much more adaptable. And there’s a pediatric endourologist there who did PCNLs on pediatric patients. To be honest, we didn’t do a lot of the procedures that I do now. I kind of adapted some of the techniques that I learned. And with the support of the pediatric department and the pediatric urologists with whom I work very closely, we have been very successful in identifying the right patients and – touch wood – the patients are doing very well.
What important findings regarding miniPCNL in pediatric patients would you like to share?
The main thing I want to get out of the way is that it’s a very invasive and very dangerous procedure. That’s one of the reasons why I often see patients in children not getting the most effective procedure. They’re more likely to get minimally invasive, potentially less effective procedures, and multiple of them. It’s not because people don’t want to do the right thing for the patient. It’s because they’re anxious, and when people are small, we don’t want anything to go wrong, and that’s a very good reason. But what I want to tell you is that even multiple procedures are not without risks. And the more procedures that are done in the ureter, the more likely you are to have scar tissue later on or to be left with a stent for a longer period of time. And I think the really beautiful thing about these minimally invasive PCNL procedures is that they’ve been shown, especially in adults, to cause fewer complications than maximally invasive PCNL procedures, but sometimes even compared to ureterorenoscopy.
The fact that we’re getting smaller and smaller and maintaining that efficacy is very helpful to patients and helps us prove, at least at this point, that this can be done safely. And that’s the main thing I usually try to dispel – this idea that everything we do through the back is going to be associated with these older methods of percutaneous nephrolithotomy and that that gets everyone’s attention and maybe fear.
I would say you definitely have to be very adaptable. You need a great team, a great pediatric team and great pediatric colleagues if you’re not a pediatric urologist yourself. You need a great anesthesia team that’s very supportive and you have to have a wide range of tools available in case something unexpected happens, like a ureteral obstruction or an ectopic ureter or something like that, because unfortunately these kids form stones for a reason and you just have to be prepared to deal with the unexpected.
The cases that I’ve treated here have been, I think, some of the most impactful and make me really proud and happy to be a urologist and to do something that patients are incredibly grateful for. Most of these patients have lived with stents for a long time and have had to undergo multiple procedures. It’s very remarkable how tough a lot of these kids are and how well they get through these procedures and how good of a spirit they usually are. I think that’s something that’s very gratifying and I think with smaller and better devices that are constantly being developed and different techniques that are constantly being advanced, we’re just getting better and better and hopefully we can save a lot of these kids who are unfortunate enough to develop stones a lot of suffering in the future.
